Oscar Pistorius's defence team has picked through the testimony of a police photographer who took images of the bloodied crime scene where the Paralympian shot dead his girlfriend.

The South African "Blade Runner" denies the premeditated murder of Reeva Steenkamp on Valentine's Day last year, saying he shot her in a tragic accident after mistaking her for a night-time intruder.

On day 12 of the trial, defence lawyer Barry Roux accused police photographer Bennie van Staden of "great disturbance" for moving evidence, and also pointed out suspicious timing overlaps that seemed to contradict Mr Staden's testimony.

Mr Staden moved bloodied towels and a duvet, which he said was to check for evidence beneath the objects.

He said he always took pictures of the original scene.

This did not deter Mr Roux, who has hammered away with the argument that police bungles tainted the crime scene so much that the evidence cannot be used against Pistorius.

"How does it happen there was such great disturbance in that scene?" he asked about pictures showing that bedsheets had been moved.

He also said metadata on crime scene photos suggested a "great overlap" in the times photographers documented the scene, contradicting testimony that they worked separately.

"You were taking photos together in the bedroom and bathroom," Mr Roux told Mr Staden, who had earlier testified that he was alone when he documented the bathroom where Steenkamp was shot dead.

Pistorius, 27, sat reading a book in court, occasionally underlining something with a pencil.

His defence team has so far pointed out several police bloopers at the crime scene, including an officer handling the suspected murder weapon without gloves and another stealing from the house.

The defence alleges that changes to the scene make it difficult to prove the sequence of events in the early morning hours on February 14 last year.

The athlete says he was convinced he was shooting at an intruder when he fired four bullets through a locked toilet door, three of which hit Steenkamp.

The first photographs of Pistorius after the shooting were displayed in court last week, showing the heavily muscled athlete bare-chested and staring vacantly at the camera, with blood spattered on his rumpled shorts and left arm.

Pistorius had his lower legs amputated as a baby, but he overcame the disability to become the "fastest man on no legs", running on carbon-fibre "blades" to win gold medals at the Beijing and London Paralympics.

He also reached the 400 metres semi-finals at the London Games, competing against able-bodied athletes.

He was not wearing his artificial legs at the time of the shooting, and has said this made him feel vulnerable and panicky, part of the reasoning behind his plea of not guilty to the murder of law graduate and model Steenkamp.